Substrates containing latent images have been used in the business forms market for producing security documents. The components used to develop images for the business forms are often self-contained in the forms typically by using microcapsules which are rupturable upon impact or contact with a suitable solvent. One such self-contained coating is described in U.S. Pat. No. 5,250,492 to Dotson et al. which relates to carbonless coating compositions for use with business forms or mailers. The business forms described by Dotson et al. are made using an admixture of a color former, a color developer, and a plurality of pressure-rupturable microcapsules containing solvent. A latent image printed with the admixture becomes visible upon application of pressure or solvent to the coated area to rupture or dissolve the microcapsules so that the solvent in the microcapsules interacts with the color developers and color formers in the coating.
While the methods and compositions of Dotson et al. are particularly suitable for business forms, they are not particularly suitable for preparing games and novelty products which contain hidden or latent multicolor images. Inadvertent rupture of the microcapsules containing solvent may result in image development particularly in unintended areas of the form while handling or shipping the form. Furthermore, it is difficult and expensive to prepare multi-color latent images using microcapsule technology to provide a color density required to maximize the color intensity for use in novelty products. For example, it is generally cost prohibitive to use microcapsule technology to produce low cost children's books, games, puzzles, activity sets, and the like in high volume with a color intensity that would be suitable for such children's items. Such products made by conventional techniques typically require heavy ink coverage to obtain suitable color intensities. Accordingly, improvements in hidden image technology are required to achieve the desired level of reliability and image sharpness and intensity and to reduce the expense and production difficulty of multi-color latent image products for the novelty and game markets.
With regard to the foregoing and other objects and advantages thereof, exemplary embodiments of the disclosure provide a latent image developing system, methods for imaging and developing images, and systems and methods for blocking or concealing latent images. The latent image developing system includes a substrate containing a colorless image deposited thereon. A developer instrument is used to provide a visible image. The developer instrument includes a developer composition reactive with the colorless image. An image blocking instrument is provided for concealing at least a portion of the visible image. The image blocking instrument is provided by a blocking composition applicator and an aqueous mixture of blocking composition and water.
Another embodiment of the disclosure provides a latent image blocking system. The latent image blocking system includes a substrate containing a developer composition deposited thereon. At least one marking instrument having a substantially colorless compound reactive with the developer composition is provided to produce a visible image on the substrate. An image blocking instrument for preventing development of at least a portion of the visible image is also included. The image blocking instrument includes a blocking composition applicator and an aqueous mixture of a blocking composition and water.
Other embodiments of the disclosure provide a method for selectively concealing a latent image developed on a substrate. The method includes providing a substrate containing a substantially colorless image deposited thereon. At least a portion of the colorless image is developed into a visible image by applying a developer composition with a developer instrument to the colorless image on the substrate to provide the visible image. An image concealing composition is applied to at least a portion of the visible image to conceal a portion of the visible image.
Still another embodiment of the disclosure provides a system for printing and developing a colorless image on a substrate. The system includes a substantially colorless flexographic ink base comprising a binder resin and from about 5 to about 20 percent by weight of a substantially colorless compound dissolved in a solvent portion of the ink base for printing the colorless image on the substrate. A developer instrument containing a developer compound dissolved in from about 65 to about 85 percent isopropyl alcohol is also provided.
An advantage of the systems, compositions, and methods described herein is that the images may be rapidly developed with high color intensity without having to apply relatively heavy ink coverage to a substrate to obtain the high color intensity images. The compositions and methods described herein are substantially more compatible with high speed printing techniques, such as four color processing, than conventional microcapsule latent image technology, and thus may provide optimum ink coverage with enhanced color intensity over conventional latent image printing technology. Accordingly, high volume, low cost activity sets, books, games, novelty items, and the like may be provided using the systems, methods and compositions described herein.
Another advantage of the compositions and methods described herein is that each of the components is substantially colorless until applied to a previously printed or coated substrate. Accordingly, the marking instruments and compositions may not stain or mark clothing, skin, furniture, walls or other objects.
Still another advantage of the embodiments described herein is the ability to provide clandestine messages by selective blocking development of latent images on a substrate.